Rocket company develops massive catapult to launch satellites into space without using jet fuel

[muriel_volestrangler]

9. An article describing the anticipated problems

https://bigthink.com/starts-with-a-bang/physics-spinlaunch/

Basically, what they've done so far is one third the radius, and about a fifth of the launch speed. Scaling up is not just a question of a bigger motor or more time to get up to speed. They might not be able to build a liquid-fuelled 2nd stage that can withstand the 5-10,000g (lateral) acceleration. Solid rocket 2nd stages aren't so controllable for the final injection into the correct orbit. The difference between a projectile breaking through a membrane from the vacuum inside the spinner to ground-level atmosphere at a little over Mach 1, and at the desired Mach 6, are considerable.

That article also mentions 'Green Launch', a project trying to achieve the same thing by launching from a hydrogen-fuelled gun - see https://www.aerospacetestinginternational.com/features/can-we-reach-space-a-different-way-by-the-end-of-this-decade.html and https://newatlas.com/space/greenlaunch-space-cannon-gas-launch/